1. Field of the Invention
The present invention relates to a dynamoelectric machine such as an automotive alternator, etc., and particularly relates to a stator winding mounting construction for a stator core in which slots are formed at a ratio of two slots per phase per pole.
2. Description of the Related Art
Conventional automotive alternators have included a stator that is formed by mounting a stator winding into a cylindrical stator core in which slots that extend axially are formed at a uniform angular pitch circumferentially; and a rotor that is disposed on an inner peripheral side of the stator, and that has a field coil. It is known that by forming the slots at a ratio of two slots per phase per pole, occurrences of surges in magnetic flux can be suppressed, fluctuations in generated voltage and output waveform disturbances can be reduced, and ripples can also be reduced when the alternating-current output from the stator is rectified into direct current.
Conventionally, from the viewpoint of stator productivity improvements and price reductions when mounting a stator winding into a stator core in which slots are formed at a ratio of two slots per phase per pole, methods have been proposed in which star-shaped winding units are prepared by forming into star shapes winding units that have been prepared by winding conductor wires into annular shapes, and the star-shaped winding units are mounted into the stator core in multiple layers (see Patent Literature 1, for example). In conventional automotive alternators such as that described in Patent Literature 1, star-shaped winding units that constitute six phase windings in two three-phase alternating-current windings are mounted into the stator core so as to be stacked in six layers radially so as to allow for balance in radial positions of coil ends to suppress power generation failure and declines in output.
Patent Literature 1: Japanese Patent No. 3484412 (Gazette)
However, in conventional automotive alternators such as that described in Patent Literature 1, because the coil ends of the six phase windings line up in six layers radially, radially outer coil ends are less likely to be exposed to cooling airflows, and winding temperature increases in the radially outer windings. Thus, winding resistance in each of the phase windings differs, giving rise to phase voltage differences, and one problem has been that fifth order and seventh order harmonic components are not canceled out completely, giving rise to magnetic noise.